Bonding layer in a semiconductor device

ABSTRACT

A semiconductor chip is bonded on a radiator plate consisting of copper material with interposition of a bonding layer having a total thickness of 80 μm comprising a laminated structure including a thermoplastic film bonding layer  12   a  having a thickness of 50 μm and a paste-based bonding layer  12   b  having a thickness of 30 μm. For example, butadiene-modified polyolefin-based adhesive resin mixed with alumina fine power is used as material of the thermoplastic film bonding layer  12   a,  and, for example, silicone rubber-modified epoxy-based adhesive resin mixed with silver powder is used as material of the paste-based bonding layer  12   b.  There is thus provided a semiconductor device having a semiconductor chip bonded on a radiator plate with interposition of a bonding layer, wherein stress concentration caused in the bonding layer is relaxed and heat dissipation performance is maintained and thus the reliability in endurance is high, and a method for manufacturing the semiconductor device.

RELATED APPLICATION DATA

The present application claims priority to Japanese Application No.P10-226201 filed Aug. 10, 1998 which application is incorporated hereinby reference to the extent permitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a semiconductor device and a manufacturingmethod thereof and more particularly to a semiconductor device having asemiconductor chip bonded on a radiator plate with interposition of abonding layer.

2. Description of the Related Art

It has been required that consumer appliances are made compact and therequirement has called for one chip structuring of a semiconductordevice or high density mounting of a semiconductor device, and thus areaarray packages such as ball grid array, in which external connectingterminals are arranged in the form of two-dimensional area (referred tosimply as “BGA” hereinafter), and land grid array (referred to simply as“LGA” hereinafter) have been proposed and practically used to satisfythe requirement for multi-pin semiconductor.

As a related area package, tape BGA (Tape-BFA, referred to simply as“T-BGA” hereinafter), in which TAB (Tape Automated Bonding) is used asinterconnection technique, is described referring to FIG. 2.

For example, a semiconductor chip 44 is bonded on a radiator plate 40consisting of copper material with interposition of a paste bondinglayer 42. Many electrode pads 46 are formed on the surface of thesemiconductor chip 44.

On the circumference of the radiator plate 40 surrounding thesemiconductor chip 44, a stiffener 50 is bonded with interposition of abonding layer 48. On the stiffener 50, many external connectingterminals 54 having a ball-shaped end respectively are arrangeddispersedly in the form of array.

These many external connecting terminals 54 are connected to theelectrode pads on the semiconductor chip 44 with interposition ofrespective inner leads 56. These many external connecting terminals 54are covered with an insulating film 58 excepting the ball-shaped endsand insulated stably each other. As described herein above, the externalconnecting terminals 54, inner leads 56, and insulating film 58constitute a wiring pattern 60 for connecting the electrode pads of thesemiconductor chip 44 to the external.

The semiconductor chip 44 bonded on the radiator plate 40 withinterposition of the paste bonding layer 42 and the inner leads 56connected to the electrode pads 46 are covered with sealing resin 62,this is so-called resin sealing.

As described herein above, in the T-BGA, because many externalconnecting terminals 54 are arranged dispersedly in the form of array onthe stiffener 50 surrounding the semiconductor chip 44, the package sizeof a T-BGA is made small even if the pitch of the external connectingterminals 54 of the semiconductor device having many pins is relativelylarge, for example, 1.0 mm or 0.27 mm, therefore this structure iseffective for high density mounting.

Further, the semiconductor chip 44 is bonded directly on the radiatorplate 40 with interposition of the paste bonding layer 42, and thereforeheat generated from the semiconductor element during operation is easilydissipated, thus this structure is also effective for low heatresistance packaging.

However, in the above-mentioned T-BGA, the thermal expansion coefficientof the semiconductor chip 44 is approximately 3 ppm/° C. and the thermalexpansion coefficient of the radiator plate 40 consisting of coppermaterial is approximately 17 ppm/° C., the large difference in thethermal expansion coefficient between both components causes the stressconcentration on the paste bonding layer 42 between the semiconductorchip 44 and the radiator plate 40, for example, when the semiconductordevice is subjected to a thermal cycle test (referred to simply as T/Ctest hereinafter), in which the temperature of the T-BGA is variedcyclically, the bonding strength of the paste bonding layer 42 isdecreased to cause cracking or separation occasionally at the end.

As described herein above, though the semiconductor device is excellentin heat dissipation initially as it is fabricated, after T/C test, thebonding strength of the paste bonding layer 42 which has been subjectedto stress concentration is decreased, and good contact between thesemiconductor chip 44 and the radiator plate 40 is deteriorated toresult in significantly reduced heat dissipation, and thus thereliability in endurance becomes poor disadvantageously.

Not only T-BGA but also semiconductors of other types as long as abonding layer is provided between a semiconductor chip and a radiatorplate or a die pad consisting of copper material are involved generallyin the problem.

SUMMARY OF THE INVENTION

The present invention has been accomplished to solve the above-mentionedproblem, and the object of the present invention is to provide asemiconductor device having a semiconductor chip bonded on a radiatorplate with interposition of a bonding layer in which stressconcentration caused in the bonding layer is relaxed to maintain theheat dissipation performance and which is excellent in reliability inendurance and a method for manufacturing thereof.

The inventors of the present invention examined the reduction of stressconcentration caused in a bonding layer between bonded bodies formed ofdifferent materials due to the difference in thermal expansioncoefficient between these materials to solve the above-mentionedproblem.

In general, sufficiently thick thickness of a bonding layer is requiredto relax stress concentration on the bonding layer to be providedbetween a semiconductor chip and a radiator plate which have thedifferent thermal expansion coefficient each other. However, it isdifficult to form an even bonding layer having a sufficient thicknesswith a single layer of a related paste-based bonding layer, and abonding layer having the sufficiently thick thickness can not berealized.

To secure an even bonding layer having a thickness sufficient for thebonding layer to relax stress concentration caused on the bonding layer,the inventors tried to use a thermoplastic film bonding layer instead ofpaste-based bonding layer. In this case, though it was easily achievedto form an even bonding layer having a sufficient and necessarythickness, the bonding layer was involved in the problem of blisteringin at least any one of interfaces between a semiconductor chip and thethermoplastic film bonding layer or a radiator plate and thethermoplastic film bonding layer when the thermoplastic film bondinglayer placed between a semiconductor chip of a hard material and aradiator plate of a hard material was press-bonded together. In detail,though no blistering was not caused when a thermoplastic film bondinglayer was bonded on a semiconductor chip or a radiator plate, however,it was very difficult to prevent blistering when a radiator plate or asemiconductor chip was press-bonded on the thermoplastic film bondinglayer bonded on the semiconductor chip or the radiator plate. Theexistence of the blister resulted in reduced bonding strength andreduced heat dissipation performance of the bonding layer.

Experiments were repeated to find a bonding layer for forming an evenbonding layer having a necessary and sufficient thickness to relaxstress concentration by a method in which blistering was prevented so asnot to cause reduction of bonding strength and reduction of heatdissipation performance. As the result, the semiconductor device and themethod for manufacturing thereof in accordance with the presentinvention has been accomplished.

In detail, a semiconductor device in accordance with one aspect of thepresent invention is a semiconductor device having a semiconductor chipbonded on a radiator plate with interposition of a bonding layer,wherein the bonding layer comprises a laminated structure including athermoplastic film bonding layer and a paste-based bonding layer.

In the semiconductor device in accordance with one aspect of the presentinvention, because the laminated structure including the thermoplasticfilm bonding layer and the paste-based bonding layer is employed as thebonding layer for bonding the semiconductor chip on the radiator plate,an even bonding layer having a necessary and sufficient thickness isformed, and blistering, which causes reduction of bonding strength andreduction of heat dissipation of the bonding layer, is prevented.

In other words, the thermoplastic film bonding layer is served to securethe necessary and sufficient thickness of the bonding layer and tosecure the evenness of the bonding layer, and on the other hand, thepaste-based bonding layer formed of soft material which is provided onthe one side of the thermoplastic film bonding layer is served toprevent blistering when the bonding layer is press-bonded together withthe thermoplastic film bonding layer.

The semiconductor device in accordance with another aspect of thepresent invention is a semiconductor device described in theabove-mentioned claim 1, wherein the total thickness of thethermoplastic film bonding layer and the paste-based bonding layer is ina range from 50 to 150 μm, and the stress concentration suppressioneffect is thereby improved while the heat dissipation effect of thebonding layer having the two layer structure is maintained.

In detail, the total thickness of the thermoplastic film bonding layerand the paste-based bonding layer thinner than 50 μm results in reducedstress concentration suppression effect on the bonding layer having thetwo layer structure though the heat dissipation effect is improved, forexample, the excellent contact between the semiconductor chip and theradiator plate is deteriorated and the heat dissipation performance isdecreased after T/C testing, and the reliability in endurance thereforebecomes poor. On the other hand, the total thickness of thethermoplastic film bonding layer and the paste-based bonding layerthicker than 150 μm results in reduced heat dissipation effect thoughthe stress concentration suppression effect on the bonding layer havingthe two layer structure is improved. Accordingly, the total thickness ofthe thermoplastic film bonding layer and the paste-based bonding layerof 50 to 150 μm is preferable to improve the stress concentrationsuppression effect while the heat dissipation effect of the bondinglayer having the two layer structure is improved.

The thickness of the thermoplastic film bonding layer is preferably in arange form 20 to 100 μm and the thickness of the paste-based bondinglayer is preferably in a range from 10 to 70 μm while the totalthickness of the bonding layer having the two layer structure is in arange from 50 to 150 μm.

The semiconductor device in accordance with another aspect of thepresent invention is a semiconductor described in the above-mentionedclaim 1, wherein the thermoplastic film bonding layer is modified orblended with rubber-based material. For example, polyolefin-based orpolyimide-based thermoplastic resin is modified or blended with siliconerubber, butadiene rubber, urethane rubber, or acrylic rubber, and thefilm-like thermoplastic resin bonding layer is thereby rendered soft andlow in the elastic modulus, thus the larger stress concentrationrelaxation effect is brought about with the thinner thickness.Particularly the thermoplastic film bonding layer having the elasticmodulus of 1 GPa or lower at a room temperature and the elastic modulusof 3 GPa or lower at −25° C. is more effective in stress concentrationsuppression.

The semiconductor device in accordance with another aspect of thepresent invention is a semiconductor described in the above-mentionedclaim 1, wherein ceramic fine powder or metal powder is mixed in thethermoplastic film bonding layer. The ceramic fine powder or metal poweris served to improve the thermal conductivity of the thermoplastic filmbonding layer, and thereby brings about the more improved heatdissipation performance. Examples of ceramic fine powder include, forexample, fine powder of alumina, silica, and silicon nitride, andexamples of metal powder include, for example, silver powder andaluminum powder.

Further, the semiconductor device in accordance with another aspect ofthe present invention is the above-mentioned semiconductor, wherein thepaste-based bonding layer is mixed with fine powder filler. For example,the fine powder filler such as silver powder or silica powder is mixedin epoxy resin or silicone resin, and thereby improves the bondingstrength and thermal conductivity of the paste-based bonding layer.

Further, the semiconductor device in accordance with another aspect ofthe present invention is a semiconductor device described above, whereinthe paste-based bonding layer is formed of epoxy-based adhesive resin,and the epoxy-based adhesive resin is modified or blended withrubber-based material. For example, epoxy-based adhesive resin ismodified or blended with silicone rubber, butadiene rubber, urethanerubber, or acrylic rubber, then the elastic modulus is thereby reduced,and such epoxy-based adhesive resin exhibits the more stressconcentration relaxation effect with the thinner thickness.Particularly, the paste-based bonding layer having an elastic modulus of1 GPa or lower at a room temperature exhibits the marked stressconcentration relaxation effect.

Further, a method for manufacturing a semiconductor device in accordancewith another aspect of the present invention comprises a step forcoating a paste-based bonding layer on the back side of thesemiconductor chip, a step for bonding a thermoplastic film bondinglayer on a radiator plate, and a step for heat-press-bonding thepaste-based bonding layer coated on the back side of the semiconductorchip and the thermoplastic film bonding layer bonded on the radiatorplate together.

In the method for manufacturing a semiconductor device in accordancewith another aspect of the present invention as described herein above,the paste-based bonding layer coated on the back side of thesemiconductor chip and the thermoplastic film bonding layer bonded onthe radiator plate are heat-press-bonded together to thereby form aneven bonding layer having a necessary and sufficient thicknesscomprising the laminated structure including the thermoplastic filmbonding layer and the paste-based bonding layer. In this case,blistering, which causes reduction of bonding strength and reduction ofheat dissipation performance of the bonding layer, is prevented becausethe thermoplastic film bonding layer is bonded on the radiator plate andthen the exposed side is heat-press-bonded to the paste-based bondinglayer of soft material, differently from the case that the bonding layeris placed directly between the semiconductor chip and the radiator plateof hard material and press-bonded together.

A method for manufacturing a semiconductor device in accordance withanother aspect of the present invention comprises a step for bonding athermoplastic film bonding layer on a radiator plate, a step for coatinga paste-based bonding layer on the thermoplastic film bonding layer, anda step for press-bonding the semiconductor chip on the paste-basedbonding layer.

In the method for manufacturing a semiconductor in accordance withanother aspect of the present invention, as described herein above, thepaste-based bonding layer is bonded on the thermoplastic film bondinglayer bonded on the radiator plate to thereby form an even bonding layerhaving a necessary and sufficient thickness comprising the laminatedstructure including the thermoplastic film bonding layer and thepaste-based bonding layer. Because the paste bonding layer of softmaterial is coated on the exposed surface of the thermoplastic filmbonding layer after the thermoplastic film bonding layer has been bondedon the radiator plate, blistering, which causes reduction of bondingstrength and reduction of heat dissipation performance of the bondinglayer, is prevented, diffidently from the case that the bonding layer isplaced directly between the semiconductor chip and the radiator plate ofhard material and then press-bonded together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view for illustrating T-BGA inaccordance with one embodiment of the present invention.

FIG. 2 is a schematic cross sectional view for illustrating the relatedT-BGA.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment of the present invention will be described in detailhereinafter with reference to the attached drawings.

FIG. 1 is a schematic cross sectional view for illustrating a T-BGA inaccordance with one embodiment of the present invention.

A semiconductor chip 14 is bonded on a radiator plate 10 consisting of,for example, copper material with interposition of a bonding layer 12having a total thickness of 80 μm comprising two layer structure of athermoplastic film bonding layer 12 a having a thickness of 50 μm and apaste bonding layer 12 b having a thickness of 30 μm. A plurality ofelectrode pads 16 are formed on the surface of the semiconductor chip14. For example, a polyolefin-based adhesive resin modified withbutadiene rubber mixed with alumina fine powder is used as the materialof the thermoplastic film bonding layer 12 a, and, for example, aepoxy-based adhesive resin modified with silicone rubber mixed withsilver powder is used as the material of the paste-based bonding layer12 b.

A stiffener 20 is bonded on the radiator plate 10 surrounding thesemiconductor chip 14 with interposition of a bonding layer 18. Aplurality of external connecting terminals 24 having a ball-shaped endare arranged dispersedly in the form of array on the stiffener 20 withinterposition of a bonding layer 22.

The plurality of external connecting terminals 24 are connected to theelectrode pads 16 provided on the surface of the semiconductor chip 14with interposition of respective inner leads 26. The plurality ofexternal connecting terminals 24 are covered with an insulating film 28excepting the ball-shaped ends, and are insulated stably each other. Theplurality of external connecting terminals 24 having a ball-shaped end,inner leads 26 connected to the respective external connecting terminals24, and the insulating film 28 which covers these external connectingterminals 24 excepting the ball-shaped ends constitute a wiring pattern30 for connecting the electrode pads 16 of the semiconductor 14 to theexternal.

The semiconductor chip 14, which is bonded on the radiator plate 10 withinterposition of the bonding layer 12 comprising the laminated structureincluding the thermoplastic film bonding layer 12 a and the pastebonding layer 12 b, and the inner leads 26 connected to the respectiveelectrode pads 16 are covered with the sealing resin 32 and resinsealed.

Next, the first fabrication process of the T-BGA is described.

First, the wiring pattern 30 comprising the plurality of externalconnecting terminals 24 having a ball-shaped end, the inner leads 26connected to the respective external connecting terminals 24, and theinsulating film 28, which covers the respective connecting terminals 24excepting ball-shaped ends, is heat-press-bonded on the stiffener 20with interposition of the bonding layer 22. The plurality of externalconnecting terminals 24 having a ball-shaped end are arrangeddispersedly in the form of array on the stiffener 20 as described hereinabove.

Next, the semiconductor chip 14 is bonded on the radiator plate 10consisting of copper material at a predetermined position withinterposition of the bonding layer 12 comprising the laminated structureincluding the thermoplastic film bonding layer 12 a and the paste-basedbonding layer 12 b. In this case, two methods are employable.

In one method of the two, the paste-based bonding layer 12 b consistingof epoxy-based adhesive resin modified with silicone rubber having athickness of 30 μm is coated on the back side of the semiconductor chip14. Further, the thermoplastic film bonding layer 12 a consisting ofpolyolefin-based adhesive resin modified with butadiene rubber having athickness of 50 μm is bonded on the radiator plate 10 at a predeterminedposition. Subsequently, the paste-based bonding layer 12 b coated onthe-based side of the semiconductor 14 and the thermoplastic filmbonding layer 12 a bonded on the radiator plate 10 are heat-press-bondedtogether.

In the other method of the two, the thermoplastic film bonding layer 12a consisting of polyolefin-based adhesive resin modified with butadienerubber having a thickness of 50 μm is bonded on the radiator plate 10 ata predetermined position. Subsequently, the paste-based bonding layer 12b consisting of epoxy-based adhesive resin modified with silicone rubberhaving a thickness of 30 μm is coated on the thermoplastic film bondinglayer 12 a. Further, the semiconductor chip 14 is press-bonded on thepaste-based bonding layer 12 b.

Next, the stiffener 20 on which the wiring pattern 30 has beenpress-bonded is aligned and then bonded on the radiator plate 10surrounding the semiconductor chip 14 with interposition of the bondinglayer 18. Subsequently, the inner leads 26 of the wiring pattern 30 areconnected to the electrode pads 16 on the surface of the semiconductorchip 14. As described herein above, the electrode pads 16 on the surfaceof the semiconductor chip 14 are connected to the external connectingterminals 24 by way of the inner leads 26 by inner lead bonding.

Next, the semiconductor chip 14 bonded on the radiator plate 10 withinterposition of the bonding layer 12 comprising the laminated structureincluding the thermoplastic film bonding layer 12 a and the paste-basedbonding layer 12 b and the inner leads 26 connected to the respectiveelectrode pads 16 are covered with the sealing resin 32 and resinsealed. Thus the T-BGA shown in FIG. 1 is fabricated.

Next, the second fabrication method of T-BGA shown in FIG. 1 isdescribed.

First, the wiring pattern 30 comprising the plurality of externalconnecting terminals 24 having a ball-shaped end, the inner leads 26connected to the respective external connecting terminals 24, and theinsulating film 28, which covers the respective connecting terminals 24excepting ball-shaped ends, is press-bonded on the stiffener 20 withinterposition of the bonding layer 22. The plurality of externalconnecting terminals 24 having a ball-shaped end are arrangeddispersedly in the form of array on the stiffener 20 as described hereinabove.

Next, the inner leads 26 of the wiring pattern 30 which is press-bondedon the stiffener 20 is connected to the electrode pads 16 on the surfaceof the semiconductor chip 14 by inner lead bonding. As described hereinabove, the electrode pads 16 on the surface of the semiconductor chip 14are connected to the respective external connecting terminals 24 by wayof the respective inner leads 26.

Next, the semiconductor chip 14 is bonded on the radiator plate 10 at apredetermined position with interposition of the bonding layer 12comprising the laminated structure including the thermoplastic filmbonding layer 12 a and the paste-based bonding layer 12 b, and thestiffener 20 is bonded on the radiator plate 10 surrounding thesemiconductor chip 14 with interposition of the bonding layer 18. Twomethods are employable also in this case.

In one method, the paste-based bonding layer 12 b consisting ofepoxy-based adhesive resin modified with silicone rubber having athickness of 30 μm is coated on the back side of the semiconductor chip14. The thermoplastic film bonding layer 12 a consisting ofpolyolefin-based modified with butadiene rubber having a thickness of 50μm is bonded on the radiator plate 10 at the position where thesemiconductor chip 14 is to be mounted, and the bonding layer 18 iscoated on the radiator plate 10 surrounding the place where thesemiconductor chip 14 is to be mounted. Subsequently, the paste-basedbonding layer 12 b coated on the back side of the semiconductor chip 14and the thermoplastic film bonding layer 12 a bonded on the radiatorplate 10 are heat-press-bonded together, and the stiffener 20 ispress-bonded on the bonding layer 18 coated on the radiator plate 10.

In the other method, the thermoplastic film bonding layer 12 aconsisting of polyolefin-based adhesive resin modified with butadienehaving a thickness of 50 μm is bonded on the radiator plate 10 at theplace where the semiconductor chip 14 is to be mounted. Subsequently,the paste-based bonding layer 12 b consisting of epoxy-based adhesiveresin modified with silicone rubber having a thickness of 30 μm iscoated on the thermoplastic film bonding layer 12 a. The semiconductorchip 14 is thereafter press-bonded on the paste-based bonding layer 12 bcoated on the thermoplastic film bonding layer 12 a, and the stiffener20 is press-bonded on the bonding layer 18 coated on the radiator plate10.

Next, the semiconductor chip 14 bonded on the radiator plate 10 withinterposition of the bonding layer 12 comprising the laminated structureincluding the thermoplastic film bonding layer 12 a and the paste-basedbonding layer 12 b and the inner leads 26 connected to the respectiveelectrode pads of the semiconductor chip 14 are covered with the sealingresin 32 and resin sealed. Thus the T-BGA shown in FIG. 1 is fabricated.

Next, the T/C test result on the T-BGA in accordance with the presentembodiment shown in FIG. 1 is described.

In the T/C test, the high temperature side temperature was set to 125°C. and the low temperature side temperature was set to −55° C. Four setsof conditions for thermal cycling namely the number of cycles of 200,400, 600, and 1000 were used. Ten test T-BGAs shown in FIG. 1 werefabricated and these Ten T-BGAs were subjected to the test. Forcomparison, Ten related T-BGAs as shown in FIG. 2 were fabricated andthese related 10 T-BGAs were also subjected to the same T/C test.

The number of defectives caused in the laminated structure including thethermoplastic film bonding layer 12 a and the paste-based bonding layer12 b of the T-BGAs in accordance with the present embodiment shown inFIG. 1 and the number of defectives caused in the paste-based bondinglayer 42 of the related T-BGAs shown in FIG. 2 in the T/C test are shownin Table 1.

TABLE 1 The number of defectives Thermal cycles 200 400 600 1000 T-BGA0/10 0/10 0/10 0/10 according to the present embodiment Related T-BGA0/10 2/10 10/10 —

As obviously shown in the T/C test result in Table 1, zero test pieceout of 10 T-BGA in accordance with the present invention shown in FIG. 1are defective due to cracking or separation in the bonding layer 12comprising laminated structure including the thermoplastic film bondinglayer 12 a and the paste-based bonding layer 12 b after 1000 repeatedthermal cycles, that is, no defective was caused.

On the other hand, in the case of the related T-BGAs shown in FIG. 2,though no defect was caused after 200 repeated thermal cycles, twodefectives were caused after 400 repeated thermal cycles, and 10defectives were caused after 600 repeated thermal cycles, that is, allthe test pieces were defective.

As described herein above, according to the present embodiment, byheat-press-bonding the paste-based bonding layer 12 b consisting of softmaterial having a thickness of 30 μm coated on the back side of thesemiconductor chip 14 and the thermoplastic film bonding layer 12 ahaving a thickness of 50 μm bonded on the radiator plate 10 together orby press-bonding the semiconductor chip 14 on the paste-based bondinglayer 12 b having a thickness of 30 μm which has been formed by coatingsoft paste-based bonding material on the thermoplastic film bondinglayer 12 a having a thickness of 50 μm bonded on the radiator plate 10,the bonding layer 12 comprising the laminated structure including atotal thickness of 80 μm, which satisfies the necessary and sufficientcondition, is formed evenly, and blistering which will cause reductionof bonding strength of the bonding layer and reduction of heatdissipation is prevented, the bonding structure described herein aboveis effective to relax stress concentration caused in the bonding layer12 comprising the two layer structure and to maintain excellent heatdissipation performance, and thus high reliability in endurance isrealized.

In the above-mentioned embodiment, the bonding layer 12 comprising thelaminated structure including the thermoplastic film bonding layer 12 aand the paste-based bonding layer 12 b having a total thickness of 80 μmis used, however the total thickness of the bonding layer 12 comprisingthe two layer thickness is by no means limited to this value, forexample, any bonding layer 12 may be used to improve the stressconcentration preventing effect while maintaining the heat dissipatingeffect on the bonding layer 12 comprising the two layer structure aslong as the total thickness is, for example, in a range from 50 μm to150 μm.

The bonding layer 12 exhibits the maximized stress concentrationrelaxing effect with a thinner thickness by employing polyolefin-basedadhesive resin modified with butadiene rubber as the material of thethermoplastic film bonding layer 12 a to form the bonding layer of asoft thermoplastic resin film by using polyolefin-based adhesive resinmodified with butadiene rubber as the material of the thermoplastic filmbonding layer 12 a so that the bonding layer is formed of softthermoplastic film resin having low elastic modulus. Further,polyolefin-based adhesive resin modified with butadiene rubber containsalumina fine powder so that the thermal conductivity is increased andthe heat dissipation performance is improved.

In the above-mentioned present embodiment, the thermoplastic resin ofpolyolefin-based adhesive resin was used as the material of thethermoplastic film bonding layer 12 a, however the material of thethermoplastic film bonding layer 12 a is no by means limited to thisresin, for example, other thermoplastic resin such as polyimide may beused. The thermoplastic resin which is modified with butadiene rubber isused in the above-mentioned present embodiment, however other polymerssuch as silicone rubber, urethane rubber, or acrylic rubber may be usedfor modification or blending. Further, fine powder of ceramics such assilica or silicon nitride, or metal fine power such as silver power oraluminum powder may be mixed instead of alumina fine powder.

The bonding strength and thermal conductivity of the paste-based bondinglayer 12 b are increased by using epoxy-based adhesive resin mixed withsilver powder as the material of the paste-based bonding layer 12 b.Because the elastic modulus is decreased by modifying epoxy-basedadhesive resin with silicone rubber, the bonding layer exhibitssignificant stress concentration relaxing effect with a thinnerthickness.

In the above-mentioned embodiment, epoxy-based adhesive resin mixed withsilver powder is used as the material of the paste-based bonding layer12 b, however the material of the paste-based bonding layer 12 b is byno means limited to this resin, for example, silicone-based adhesiveresin may be used instead of epoxy-based adhesive resin. Further, finepowder filler such as silica powder or alumina powder may be usedinstead of silver powder. Epoxy-based adhesive resin is modified withsilicone rubber in the above-mentioned embodiment, however for example,butadiene rubber, urethane rubber, or acrylic rubber may be used formodification or blending.

As described herein above, according to the semiconductor device and thefabrication method thereof in accordance with the present invention, thepresent invention exhibits the following effects.

In detail, according to the semiconductor device in accordance with theclaim 1, because the laminated structure including the thermoplasticfilm bonding layer and the paste-based bonding layer is employed as thebonding layer for bonding the semiconductor chip on the radiator plate,an even bonding layer having a necessary and sufficient thickness isformed, and blistering, which causes reduction of bonding strength andreduction of heat dissipation of the bonding layer, is prevented,further the stress concentration caused in the bonding layer is relaxedwhile the heat dissipation performance is maintained, and thus highreliability in endurance is obtained.

According to the semiconductor device in accordance with claim 2, thetotal thickness of the thermoplastic film bonding layer and thepaste-based bonding layer is in a range from 50 to 150 μm, and thestress concentration suppression effect is thereby improved while theheat dissipation effect of the bonding layer having the two layerstructure is maintained.

According to the semiconductor device in accordance with claim 3, thethermoplastic film bonding layer is modified or blended withrubber-based material. and the film-like thermoplastic resin bondinglayer is thereby rendered soft and low in the elastic modulus, thus thelarger stress concentration relaxation effect is brought about with thethinner thickness.

According to the semiconductor device in accordance with claim 4,ceramic fine powder or metal powder is mixed in the thermoplastic filmbonding layer. The ceramic fine powder or metal power is served toimprove the thermal conductivity of the thermoplastic film bondinglayer, and thereby brings about the more improved heat dissipationperformance.

According to the semiconductor device in accordance with claim 5, thepaste-based bonding layer is mixed with fine powder filler, and therebyimproves the bonding strength and thermal conductivity of thepaste-based bonding layer.

According to the semiconductor device in accordance with claim 6, theepoxy-based adhesive resin is modified or blended with rubber-basedmaterial, the elastic modulus is thereby reduced, and such epoxy-basedadhesive resin exhibits the more stress concentration relaxation effectwith the thinner thickness.

According the method for manufacturing a semiconductor device inaccordance with claim 7, the paste-based bonding layer coated on theback side of the semiconductor chip and the thermoplastic film bondinglayer bonded on the radiator plate are heat-press-bonded together tothereby form an even bonding layer having a necessary and sufficientthickness comprising the laminated structure including the thermoplasticfilm bonding layer and the paste-based bonding layer. Further,blistering, which causes reduction of bonding strength and reduction ofheat dissipation performance of the bonding layer, is prevented becausethe thermoplastic film bonding layer is bonded on the radiator plate andthen the exposed side is heat-press-bonded on the paste-based bondinglayer of soft material.

According to the method for manufacturing a semiconductor device inaccordance with claim 8, the paste-based bonding layer is bonded on thethermoplastic film bonding layer bonded on the radiator plate to therebyform an even bonding layer having a necessary and sufficient thicknesscomprising the laminated structure including the thermoplastic filmbonding layer and the paste-based bonding layer. Further, because thepaste bonding layer of soft material is coated on the exposed surface ofthe thermoplastic film bonding layer after the thermoplastic filmbonding layer has been bonded on the radiator plate, blistering, whichcauses reduction of bonding strength and reduction of heat dissipationperformance of the bonding layer, is prevented,

What is claimed is:
 1. A semiconductor device, comprising: a radiatorplate; and a semiconductor chip bonded on the radiator plate by abonding layer, wherein the bonding layer includes a laminated structurehaving a thermoplastic film bonding layer and a paste-based bondinglayer.
 2. A semiconductor device as claimed in claim 1, wherein thetotal thickness of the thermoplastic film bonding layer and thepaste-based bonding layer is 50 to 150 μm.
 3. A semiconductor device asclaimed in claim 1, wherein the thermoplastic film bonding layer ismodified with a rubber-based material.
 4. A semiconductor device asclaimed in claim 1, wherein the thermoplastic film bonding layer ismixed with one of ceramic fine powder and metal powder.
 5. Asemiconductor device as claimed in claim 1, wherein the paste-basedbonding layer includes a resin mixed with fine powder filler.
 6. Asemiconductor device as claimed in claim 2, wherein a ratio of athickness of the thermoplastic film bonding layer to a thickness of thepaste-based bonding layer is 5 to
 3. 7. A semiconductor device asclaimed in claim 1, wherein a stack is structurally arranged in thefollowing order (i) the semiconductor chip, (ii) the paste-based bondinglayer, (iii) the thermoplastic film bonding layer, and (iv) the radiatorplate.
 8. A semiconductor device as claimed in claim 1, wherein a widthof the paste-based bonding layer tapers from a width of thethermoplastic film bonding layer to a width of the semiconductor chip.9. A semiconductor device as claimed in claim 5, wherein the paste-basedbonding layer is formed of epoxy-based adhesive resin, and theepoxy-based adhesive resin is modified with a rubber-based material. 10.A semiconductor device as claimed in claim 9, wherein the thickness ofthe thermoplastic film bonding layer is 50 μm and the thickness of thepaste-based bonding layer is 30 μm.